1. Field of the Invention
The present invention relates to a starter for starting an engine, and particularly to a starter with a clutch roller movement structure.
2. Description of Related Art
A starter having a planetary gear reduction mechanism and a one-way clutch is conventionally known by, for instance, JP-U 50-45522. The structure of the planetary gear reduction mechanism and one-way clutch of such a starter is shown in FIG. 7.
The planetary gear reduction mechanism is comprised of a sun gear 110 formed on the outer member circumference of an armature shaft 100, planetary gears 120 engaging with sun gear 110, an internal gear 130 engaging with planetary gears 120, and a planet carrier 140 for rotating by receiving a revolving power of planetary gears 120. Each planetary gear 120 is supported rotatably, via a bearing 160, on the outer member circumference of a pin 150 fixed on planet carrier 140.
The one-way clutch comprises an outer member 170 integrally formed with planet carrier 140 in an axially shifting position therefrom, an inner member 190 formed on the rear end portion of an output shaft 180, and rollers 200 disposed between outer member 170 and inner member 190. A limiting plate 210 for limiting a movement of rollers 200 in the axial direction is caulked and fixed onto planet carrier 140 by a clutch cover 220.
However, since the abovementioned starter requires an additional part (clutch cover 220) other than the one-way clutch constituting members, such as outer member 170, rollers 200, inner member 190 and limiting plate 210, the number of required parts increases and the number of fitting works increases accordingly.
Also, in this starter, centering of outer member 170 is made by contacting the inner circumferential surface of planet carrier 140 with the outer circumferential surface of output shaft 180. Since this centering is performed at one side of roller 200 in the axial direction, and outer member 170 is likely to become out of balance at the time of high speed rotation, the gears of the planetary gear reduction mechanism might be damaged when an imbalanced load is added to outer member 170. To overcome this problem, a centering method of contacting the inner circumferential surface of limiting plate 210 with the outer circumferential surface of output shaft 180 at both sides of rollers 200 has been considered. In this case, since limiting plate 210 is caulked and fixed with planet carrier 140 (outer member 170) by clutch cover 220, there is a possibility that limiting plate 210 will shift in the radial direction with respect to outer member 170 and it is difficult to perform the centering surely.
Further, at the time of driving when the revolving power of planetary gears 120 is transmitted to planet carrier 140 via pins 150, a heavy load is generated at a press-fitting portion 151 of pins 150 with respect to planet carrier 140. Therefore, a length 1 of press-fitting portion 151 of pins 150 should be taken long enough. As a result, planet carrier 140 has to be designed long in the axial direction, a total length of the starter becomes long and it would bring a contrary result to a compactness requirement of the same.